Non-Dispersive Infra-Red (NDIR) is a common measurement principle for detecting gases in the environment. NDIR sensors utilize the principle that various gases exhibit substantial absorption at specific wavelengths in the infrared radiation spectrum. The term “non-dispersive” as used herein refers to the apparatus used, typically a narrow-band optical or infrared transmission filter, instead of a dispersive element such as a prism or diffraction grating, for isolating for the purpose of measurement the radiation in a particular wavelength band that coincides with a strong absorption band of a gas to be measured.
NDIR has enjoyed widespread use in gas measurement because NDIR gas sensors are highly accurate, relatively stable and easy to operate and maintain.
The present invention is concerned with addressing problems arising from use of NDIR to detect molecules in a liquid medium, rather than in gas.